Date of Award

12-2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Environmental Engineering and Science

Advisor

Miller, Shelie A

Committee Member

Lee, Cindy

Committee Member

Moysey, Stephen

Committee Member

Mobley, Catherine

Committee Member

Klotz, Leidy

Abstract

To assess the overall net impact of an emerging technology, life cycle assessment (LCA) must be accompanied by projections of adoption. Diffusion of innovation research provides tools that incorporate economic and social variables to explain and forecast integration of technologies. A switchgrass-to-ethanol case study for the southeastern U.S. is used to demonstrate methods for gauging aggregate environmental effects of an emerging energy technology. Before applying diffusion concepts, breakeven capacities are calculated for land in row crops, hay, pasture and marginal land. Breakeven curves are generated to provide upper bounds to switchgrass adoption over a range of farm-gate prices. The amount and type of land converted to switchgrass provides estimates for the total land use change effects as well as for biomass production and overall impact of the regional switchgrass-to-ethanol system, which is measured by greenhouse gas (GHG) emissions, net fossil energy, and nitrate loss. Maximum switchgrass adoption is assessed within breakeven areas for prices of $50, $100, and $150 per metric ton (Mg). Regression analysis shows that hectares of pasture and hay lands are historically not correlated with crop production profit, which suggests minimal switchgrass adoption. Land in active row crops and marginal land have historically converted land in relation to profitability of crops; consequently, switchgrass is expected to be planted on 75% of active cropland and marginal land for which it breaks even. Next, the Bass diffusion model is used to approximate the rate of adoption using previous applications of agricultural adoption. Finally, previous studies of life cycle impacts for the system are aggregated according to adoption estimates at each price. At $100 Mg -1 , switchgrass is projected to be grown on about 0.8 million hectares of land in row crops and 0.5 million hectares of the other land categories. This area of production translates to 5.4 billion liters of ethanol, which is about 9% of the gasoline consumed annually in the region. Because land use change (LUC) benefits are enhanced by primarily converting row crops to switchgrass, annual carbon dioxide equivalents of GHG emissions are reduced by about 2 billion kg CO 2 e yr-1 . About 20 years are required to reach such a production level even though national mandates are set for 2022. Including projections of behavior in environmental assessments can inform proactive policy measures that optimize effects of emerging energy technologies.

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